This invention relates to hydrocyclones.
Hydrocyclones are widely used in the mineral processing industry for classification, de-watering and de-sliming of mineral pulps and slurries and generally for separating coarse and fine fractions of such pulps and slurries. One problem which is encountered with hydrocyclones is that a misplaced coarse fraction often occurs in the overflow of the hydrocyclone issuing from its vortex finder, which means that the overflow may have to be subjected to further treatment in order to remove the misplaced coarse fraction.
It is accordingly an object of the invention to provide a hydrocyclone which seeks to overcome the above problem or which at least provides a useful improvement over prior art hydrocyclones.
According to the invention a hydrocyclone comprises an inlet head, one or more chambers located beneath the inlet head and terminating in an underflow outlet, a vortex finder located within the inlet head and an overflow outlet connected to the vortex finder, wherein the overflow outlet has a peripheral annular zone therein which receives coarse particles in the overflow outlet issuing from the vortex finder, and a secondary outlet communicating with such annular zone.
Preferably, the annular zone is formed by a double wall formation, comprising an inner wall and an outer wall which is radially outwardly spaced from the inner wall to define an annular space between the inner wall and outer wall, with the second overflow outlet communicating with such annular space. In one arrangement, the annular zone is of a double wall frusto-conical structure which tapers outwardly in a is downstream direction.
Preferably also the send overflow outlet will communicate with the annular zone towards the downstream end thereof.
The secondary outlet preferably has adjustable valve means provided therein to control the rate of flow therethrough.